In the most popular electrophotography, charging is effected by means of corona discharge such as corotron and scorotron. However, the corona discharge is disadvantageous in that products due to the discharge cause image defects such as image blur and image loss and generation of ozone causes denaturation and environmental pollution. In recent years, hydrogenated amorphous silicon photoreceptors have been proposed as long-life photoreceptors having a high sensitivity and an excellent durability. However, these hydrogenated amorphous silicon photoreceptors exhibit a higher dielectric constant than selenium photoreceptors and organic photoreceptors, and thus are disadvantageous in that when charged by corona discharge, they are subject to the generation of ozone or image blur under high humidity. In order to eliminate these disadvantages, it has been proposed to employ a contact charging process such as roller charging instead of corona discharge (as disclosed in JP-A-63-210864, JP-A-64-29875, and JP-A-2-203359 (the term "JP-A" as used herein means an "unexamined published Japanese patent application")). However, this approach leaves much to be desired in charging. Further, since the hydrogenated amorphous silicon surface is hard if a rubber roller is used as a contact charger, it is subject to abrasion that causes deterioration with time. Thus, this is an unreliable charging process for long-life photoreceptors.